Gear change mechanisms with an automatic shifting device are widely used especially in the manufacture of motor vehicles. Such shifting devices usually have an operating state R for engaging the at least one reverse gear, an operating state N for interrupting the torque transmission in the gear change mechanism, and an operating state D for engaging a forward gear. An operating state P for engaging the parking brake is additionally frequently provided.
If, e.g., the operating state D for engaging a forward gear is activated, the automatic shifting device of the gear change mechanism automatically selects the forward gear that appears most suitable from the available forward gears as a function of certain parameters of the vehicle, e.g., the instantaneous velocity or the acceleration, corresponding to one or more preset shifting programs, and controls the gear change mechanism correspondingly. The driver of the vehicle can frequently select separate shifting programs for summer and winter and/or sports driving and economic driving.
Such shifting devices are controlled by means of signal transmitters. While the control by the signal transmitter used to be performed mechanically by means of cables, electronic transmission of the signals is now preferred, because this permits the flexible arrangement of the signal transmitter. For the selection of the particular operating state R N D P of the automatic shifting device, such a signal transmitter has a gearshift lever usually provided at a center console of the vehicle. The functions of the gearshift lever corresponding to the individual operating states are arranged, as a rule, linearly in the longitudinal direction of the vehicle and can be selected by a movement of the gearshift lever in the longitudinal direction of the vehicle. In conventional signal transmitters, a function is considered to be selected only as long as the gearshift lever is located in the position designating the particular function.
A corresponding signal transmitter is described in DE 197 37 296 C2. This prior-art signal transmitter has, moreover, the possibility of leaving the automatic shifting program preset for engaging the forward gears and to shift the gears upward and/or downward manually by tapping the gearshift lever. The particular shifting operation is triggered by sending a pulse, so that the gearshift lever does not need to remain in the particular position but can automatically return into its starting position.
It is necessary for this that the automatic shifting device of the gear change mechanism be designed in the form of an electronic control device, and that the gearshift lever of the signal transmitter sends a particular control signal to the electronic control device via associated electric contacts.
Moreover, efforts have been made in recent years to replace the gearshift lever of the signal transmitter arranged at the center console with a selector lever fastened to the steering column, e.g., in order to achieve a greater freedom in designing the interior space of the vehicle.
A signal transmitter with such a selector lever is described in DE 199 16 924 A1. The operating states of the automatic shifting device of the automatically shifted transmission can be selected by deflecting the selector lever, and the selector lever can be moved along a shift gate for selecting individual functions R N D P in at least two deflection directions, and it always returns automatically into the same starting position from both deflection directions. The same operating state of the automatic shifting device of the automatically shifted transmission is assigned to each deflection direction of the selector lever in the shift gate for preselecting individual functions R N D P during the automatic operation, and two different functions can be selected in at least one deflection direction of the selector lever by the selector lever being moved over a first section up to a first stop in the deflection direction for selecting a first function, and by the selector lever being moved over a second, greater section up to a second stop in the same deflection direction for selecting a second function, while the first stop is pressed down. The individual functions are thus arranged along a straight path of movement.
The automatic shifting device of the automatically shifted transmission is controlled via impulses in this case as well, which are sent by the signal transmitter corresponding to the movement of the selector lever, so that the selector lever can return into its starting position after the selection of a function.
The drawback of the prior-art signal transmitters for setting the operating states of an automatic shifting device of a gear change mechanism with a selection means automatically returning into a normal position is that an unintended operating state may be inadvertently selected by an unintended movement over a first position (or the starting position) of the selection means.